Alternators keep failing to charge

[Raptor_]

Okay, I have to admit I'm a bit stumped on this one.

2005, 4WD V8 Explorer - EB edition.

About a month and a half ago, on the way home from a long drive in heavy traffic, I got a "Check Charging System" message, and my voltage started dropping.

My mechanic replaced the alt with a rebuilt, and a brand new battery.

A day or so later, that alt began failing to charge.

Another replacement.

This one appeared to have a bad voltage regulator, and at high RPM (such as a highway on-ramp, or passing on highway), the system seemed to overload, shutting down the instrument panel and other accessories until the RPMs dropped back to normal range.

Another replacement, and another battery too just for the hell of it since it was under a no-questions warranty.

Things seemed fine for a while. Drove for about three weeks, and around 2k miles without issue, then yesterday morning that damned "Check Charging System" light came back on. Mild, but humid weather, no AC on, no headlights on, just the radio. Voltage is confirmed to be a bit low, and very slowly dropping, but I have to believe something else is causing this to happen. Didn't have a chance to actually fix it yesterday and NEEDED to get to work this morning, so I put it on the trickle charger overnight, and did my best to use as little power as possible. Over the course of about 50 miles to, and 50 from (about an hour each way), the voltage dropped about a volt and a half, but it definitely was dropping.

Does anyone have any suggestions?

I don't have any power-hungry aftermarket equipment installed, but the weather has been nasty here recently, so I have had the AC going a lot, with both front and rear blowers on high, though it wasn't on at all yesterday morning when the light came on.

 

[Tech By Trade]

I had the same issue. it wasn't the alternator. The remote line crushed after routing the harness incorrectly. I ended up taking the entire wiring harness off, removing all the loom, cleaning up the crushed wire as well as some worn sheathing, replacing the loom and reinstalled it.Pay special attention to the fusable links. No issues since. It runs from the alternator, to the battery, with a power steering sensor off shoot, as well as an of shoot to a sensor on the block, then back to the starter. Took me half a day to do everything. Rock auto also sells entire replacement harnesses for around 100 bucks shipped.

 

[Raptor_]

I had the same issue. it wasn't the alternator. The remote line crushed after routing the harness incorrectly.

None of the wiring harnesses have been moved from their original paths. The main power supply wire that runs from the alt to the stud at the power distribution box shows good voltage and zero resistance. Visible portion of wire in crimp at the connection still appears clean and free of corrosion. Fusible links appear undamaged.

I tried jumping power to the alternator supply, as I've heard that sometimes that wire can corrode and keep the alt from turning on even if it's showing voltage, and still no success.

Is it possible that these rebuilds are actually all bad? The only other thing I can think is that the PCM isn't sending the proper charge signal to the alternator, but I would think there would be other signs if the PCM was malfunctioning.

 

[410Fortune]

Check the alt fuse?
There is a fuse for the power feed to the alternators internal voltage regulator
Fuse blown = regulator not powered = no charge

I will NEVER buy a re manufactured alternator or starter
NEW only
So many reman units fail, some right out of the box, some last for weeks, some for years.

I am not very familiar with the 05 model so forgive me if this does not apply

 

[Raptor_]

What fuse is that? I didn't find anything in the table for either fuse block that indicated anything to do with the charging system. I checked every fuse in the high-current block under the hood. They buried the other one in such a way I can't even see the damned thing without a mirror, so I haven't gone through that one as thoroughly.

I wonder if anyone has ever done a fuse block relocate on one of these?

 

[mountaineer2004]

I had Ford install a re-man alternator. It has a 2 year warranty.
Almost 2 years now, so far so good.
It was also expensive, but I was working then and made it up with overtime.
If it goes now, I'll follow 410Fortune (and others advice) and get a new one (Bosch).

 

[Raptor_]

Yeah, I've had spotty luck with remanufactured alternators in the past too, but this is FOUR of them within six weeks.

My mech swapped it out under warranty again today, and just to give one last shot at it, swapped the tensioner pulley and belt as well. At 200k miles I figured it was worth a shot, especially since it seemed loose enough that I could flex the belt enough to get it off by hand. I always remember the ones on my other 4.6's being much tighter.

If not this, our next best guess is that the PCM just isn't telling the alternator to switch on properly. :/

 

[410Fortune]

Apparently there is no more alt fuse on your model, just my luck!
I looked and looked.
good idea w the belt tension
Let us know how you make out!

 

[BrooklynBay]

Did you have the auto parts store test each one of these alternators to see what was not working (regulator, brushes, diodes, etc)?

 

[Raptor_]

Did you have the auto parts store test each one of these alternators to see what was not working (regulator, brushes, diodes, etc)?

I didn't purchase them from an auto parts store. When the first one failed, I was in a rush and it was apparent I was just barely going to make it home... if I was lucky, so I went straight to my mechanic next door (actual shop, I just happen to be fortunately close) where they swapped the alt and battery. From that point it was under warranty from their supplier, so they were taking care of the testing and exchanges. They were purchased from their usual part supplier, who gets them directly from a remanufacturer, but I haven't seen or heard the results of any testing that was done once they went back. At the shop, the only test they do is a simple voltage test while running/not running. They don't have a test stand to spin it up outside the vehicle, nor do they have the ability to check or simulate the signal from the PCM to the alternator's plug.

One of the failures I'm quite positive was a regulator failure, as it was obvious that it was producing too much power at higher RPMs - The digital portion of the dash would get brighter, the blower motor would speed up (even though it was already on high), and then I'd get a warning light and everything electronic would shut down - Identical to something I'd experienced on another Ford product when its voltage regulator failed.

 

[Tech By Trade]

Just had a look at the wiring diagram for the 05 V8. It looks like there is a feed from the PCM for control so that could be an option. The remote wire is just a feed back loop from the load side of the fusible link to the diode.

 

[Raptor_]

Just had a look at the wiring diagram for the 05 V8. It looks like there is a feed from the PCM for control so that could be an option. The remote wire is just a feed back loop from the load side of the fusible link to the diode.

Yeah, that's my fear. The connections at both ends of that data line appear relatively clean and in good condition, so I'm concerned that it may be the PCM itself. I need to take a closer look, but it looks like it might actually be accessible for replacement from the glovebox. If it comes down to that, does anyone have experience with Flagship One (dead link) They seem to have the best offer with a pre-programmed PCM and matching key blanks for around $200.

 

[Tech By Trade]

I would have to look at the altrenator diode setup, but my guess is that line isn't needed. It probably just shuts it off with a high from the PCM. The 4G alternator has been used since the early 90's with very little change and I don't think the early diodes even had that wire.

 

[Raptor_]

From what I've found while looking into it, in this particular vehicle that line from the PCM sends a square wave signal to the alternator, and the frequency of the signal determines the charging output of the alternator based on a number of factors from engine state and temperature (it has the ability to suspend charging to reduce load and stabilize RPMs during cold startup), to changes electrical demand as different systems are switched on or off. I'm wondering if that signal is not getting sent to activate the charging, and that's why I've had so many alternators stop working in such a short period of time. I've had rebuilt alternators go bad before, but not four in a row within a month and a half.

 

[Number4]

My issue was a bad connector at he alternator, causing the sense wire to send an incorrect signal to/from the PCM.

I spliced in a new connector and the issue went away.

 

[Raptor_]

Well, that's definitely a cheaper next step though I don't see anything to indicate a bad connection, it's clean and tight.

The thing I don't get is that if it is a bad connector, wire, PCM, or anything else, why does the issue go away for a period of time when a new alternator is installed?

 

[Number4]

Because you messed with the connector having the alternator changed. Same as mine. I could get out, play with the connector and it would be fine for a period of time.

 

[BrooklynBay]

Did you use a standard crimp connector to replace the connector going to the PCM or did you get a special plug from Dorman?

 

[Number4]

Did you use a standard crimp connector to replace the connector going to the PCM or did you get a special plug from Dorman?

I honestly don’t recall. It was either a non-insulated connector or a solder connection.

 

[Raptor_]

Because you messed with the connector having the alternator changed. Same as mine. I could get out, play with the connector and it would be fine for a period of time.

I had actually tried that without actually doing a swap. Removing and reinstalling the belt and unplugging, cleaning and reconnecting the plugs, but without actually swapping the alternator it didn't work.